TORONTO - A Toronto police officer shot in vain at a snowplow that was quickly barrelling down on him in the seconds before it mowed him down and left him dying in the snow, court heard Wednesday.

Several people who witnessed the death of Sgt. Ryan Russell, 35, testified at the trial of Richard Kachkar, 46, who has pleaded not guilty to charges of first-degree murder and dangerous driving in Russell's death.

The witnesses described coming upon what they at first thought was a police officer either trying to pull over a snowplow or helping it manoeuvre snowy side streets early in the morning on Jan. 12, 2011.

"It's only when I hear three gun shots that it first dawns on me that there's something amiss," Maurice Lopes testified.

Driving behind the plow, Lopes' view of the officer was blocked. But Vance Cooper, driving a short distance behind Lopes, could see Russell standing in front of his cruiser, his left arm extended and his hand up in a "stop" gesture.

But the plow didn't stop, Cooper testified, in fact, it accelerated. Cooper couldn't see a gun in Russell's hand but his right arm was extended as if he were holding one, and he heard two or three gunshots.

None of them hit the windshield of the plow, court has heard.

"At that moment the plow is bearing down on the officer and I'm just holding my breath and hoping that this officer can get out of the way," he said. "(He's) driving straight, no steering, no braking, no apparent effort to change course."

Hamid Azarbani, an electrician on his way to work that morning, testified that he had a more direct view and saw the plow hit Russell.

"I saw half of his body, almost, it was struggling on the ground and looks like (the plow) was dragging him about 15 feet," Azarbani said. "He was shaking and all of a sudden stopped."

Cooper could see a pool of blood forming around the officer's head, he testified. Two other police officers arrived on scene within minutes, court heard, but Russell was pronounced dead in hospital that morning.

Court has heard the plow hit Russell in the leg, knocking him to the ground, then hit his head, fracturing his skull.

All six lanes of Avenue Road were otherwise wide open, the witnesses testified, but the plow drove directly at the officer then continued without slowing down at all.

The judge has told the jury that there will be no dispute that Kachkar was the person driving the plow, rather the case will centre around his mental state.

The trial has already heard that Kachkar drove the plow around Toronto for two hours that morning, hitting several cars and shouting about the Taliban, Chinese technology and a microchip in his body.